A multicast (also referred to as multi-address broadcast or multicast) technology is a Transmission Control Protocol/Internet Protocol (Transmission Control Protocol/Internet Protocol, “TCP/IP” for short) network technology that allows an access point to simultaneously send a single data packet to multiple stations at a time. As one-to-many communication, multicast enables data to be simultaneously transmitted to multiple stations, and is one of effective methods that improve a throughput rate of an area and save a network bandwidth.
However, it is difficult to ensure reliability of data received by multiple stations in multicast. Because a radio channel is unreliable, a multicast frame may be lost for various reasons. For example, an access point 1 and an access point 2 run on a same channel, and two basic service sets thereof overlap. When the access point 1 sends a multicast frame to several associated stations, the access point 2 cannot detect transmission performed by the access point 1 and therefore considers that the channel is idle. Therefore, the access point 2 may transmit a multicast frame to stations associated with the access point 2. In this case, a multicast frame transmitted by the access point 1 and a multicast frame transmitted by the access point 2 are lost because of a conflict in an overlapped area of the two basic service sets. As a result, a station in the overlapped area cannot correctly receive a multicast frame. Therefore, it is extremely important to provide a multicast transmission acknowledgment mechanism.
In an existing multicast transmission acknowledgment mechanism, an access point sends several multicast frames to multiple stations in a multicast manner, and subsequently sends a multicast block acknowledgment request frame to the stations in a multicast manner; and the stations sequentially reply with multicast block acknowledgment frames according to sequence information in the multicast block acknowledgment request frame.
In a process of implementing the present invention, the inventor finds that the prior art has at least the following problem:
In an intensive scenario, when there are many multicast receiving stations, there are many multicast block acknowledgment frames, which increases a network latency and reduces a system throughput rate.